1. Field of the Invention
The present invention pertains to an image display device that scans light from a light source by means of a scanning device, and performs image display.
2. Description of the Related Art
One example of a conventional scanning device includes sympathetically vibrating mirrors, such as that disclosed in U.S. Pat. No. 5,557,444 (conventional example 1). In these sympathetically vibrating mirrors, the vibrating members are made lightweight in order to allow image display, i.e., in order to achieve a high frequency.
Another example of a conventional optical scanning device is an optical scanner disclosed in Japanese Laid-Open Patent Application Hei 5-100175 (conventional example 2). In this optical scanner, a reflective mirror is located at one end of an elastic deforming member and the linear vibration of a piezo electric element is input to a vibration input member at the other end. The reflective mirror is caused to rotationally vibrate via sympathetic vibrations with the bending and twisting vibrations of the elastic deforming member in order to deflect the light.
However, in the conventional example 1, the reflective surface is made small in order to make the mirror unit lightweight, which leads to the problem that the exit pupil is small and the position of the eye must be precisely controlled. Further, in order to achieve a higher frequency in the conventional example 1, the mirror must become even smaller, which leads to the problem that light having a numerical aperture necessary for the viewer's pupil to resolve the image cannot be provided.
Where the optical scanner of the conventional example 2 is used as a scanning device for an image display, the problems arises that, if a construction is used in which the necessary beam diameter is provided to the viewer's pupil, the size of the mirror must be increased. Because the inertial moment of the reflective mirror increases and the resonance frequency and the amplitude cannot be increased, precise and detailed images cannot be provided in a large field of view.